Natural gas powered internal combustion engines have found use in a variety of applications, for example, in generator sets that serve as primary or backup sources of electrical power. Natural gas engines also find increasingly widespread use in marine, off-highway, and locomotive applications. In particular, natural gas engines have become attractive because of their reduced emissions, smaller footprint, and relatively lower cost of operation and maintenance compared with gasoline or diesel engines. Because of the smaller engine size, however, natural gas engines may not respond to transient power demands as effectively as their gasoline or diesel powered counterparts.
One possible solution to improve the transient response capability of a natural gas engine includes using a larger displacement engine. Using a larger engine, however, increases the cost of operating and maintaining the engine, offsetting some of the cost advantages associated with the use of the smaller spark-ignited natural gas engines. Therefore, it is desirable to improve the transient response of natural gas engines to enable these engines to adequately respond to sudden and transient changes in their required power output.
SAE publication titled “A Novel System for Reducing Turbo-Lag by Injection of Compressed Gas into the Exhaust Manifold” of Cieslar et al., was published on Apr. 8, 2013 (“SAE publication”). This SAE publication discloses an exhaust assist system for improving the transient response of internal combustion engines. In the system disclosed in the SAE publication, compressed air from a reservoir is injected into the exhaust manifold of an engine to accelerate the turbocharger in situations where the engine is suddenly required to meet a higher torque output. The SAE publication discloses that its exhaust assist system is superior to intake assist systems, which inject compressed air into the intake manifold. In particular, the SAE publication points to the well-known problem of compressor surge caused when the injected compressed air enters the compressor instead of entering the combustion chambers of the engine.
Although the SAE publication discloses a system for accelerating the turbocharger to meet a sudden increase in load on the engine, the system may still be less than optimal. In particular, the disclosed system only uses the compressed air to accelerate the turbocharger. To supply sufficient power for the increased load on the engine, however, typically additional fuel is injected into the combustion chambers of the engine. In the disclosed system, however, even after acceleration using compressed air, the turbocharger compressor may not be able to supply sufficient air to combust the extra fuel, causing the engine to develop less than the required power output. This may be especially true in generator set operations where the engine may have to start from a cold start condition and deliver the desired torque output to a generator in case of a sudden and near instantaneous demand for electrical power.
The natural gas engine system of the present disclosure solves one or more of the problems set forth above and/or other problems of the prior art.